The present invention relates to a device for effectively separating gases dissolved and bubbles entrained in a liquid such as working oil, lubricant, boiler water or the like which is simple in construction, compact in size and inexpensive to manufacture.
When gases dissolved in a liquid form bubbles or when a liquid entrains bubbles, these bubbles must be separated from the liquid because they cause damage to equipment, increase compressivity, cause errosion due to cavitation, vibration and noise, result in poor product quality, and cause deterioration and change in quality of liquid.
One of the conventional methods for separating gases from a liquid is such that a liquid is stored in a tank and the gases above the level of liquid is sucked by a vacuum pump so that the pressure within the tank becomes less than a gas separation pressure (that is, a pressure at which gases dissolved in the liquid become bubbles), whereby dissolved gases are separated and floated up. Such method as described above is of a batch type so that the gas-free liquid must be refilled into another tank or the top of the tank must be opened. As a result, the operation is troublesome. In the case of air, when a liquid free from air is exposed to the surrounding atmosphere, air dissolves into the liquid again so that the dissolved air must be separated by the above-described cumbersome method.
Therefore there has been proposed a system in which a liquid is filled in an air-tightly sealed tank so that dissolved air is separated by a vacuum procedure while the liquid is suctioned by a pump. However, the tank must be provided with a vacuum pump and if the head of a liquid-discharge pump is low, the suction side becomes negative in pressure, resulting in failure to discharge the liquid. That is, a gas separation pressure of gases dissolved in a liquid held at rest is lower than a gas separation pressure of gases dissolved in a liquid in motion. As a result, in order to effect the vacuum separation of gases dissolved in a liquid contained in an air-tightly sealed tank, a negative pressure must be considerably increased. As a consequence, the head of a suction pump is decreased so that the pump cannot discharge the liquid. Therefore the pump must be placed at the upper portion of the tank so that there may be provided a sufficient head. As described above, according to the conventional air-tightly sealed tank system, the difficult problem of pressure must be investigated and solved.